早全新世沙沟河古洪水沉积及其对气候变化的响应

对沙沟河一级阶地河漫滩ZJDZ剖面中360个样品的粒度,矿物的成分含量及pH值等沉积特征进行分析,并对关键层位进行了一共6个¹⁴C年代测定。结果表明:10.9~4.0 ka B.P.期间沙沟河发生多次大规模洪水,10.9~7.0 ka B.P.期间沙沟河发生20次左右大型洪水,洪水重现期为0.40 ka,其中,10.9~9.0 ka B.P.期间洪水的规模逐次增加,9.0~7.0 ka B.P.期间洪水的规模有所减小;7.0~4.2 ka B.P.期间至少有过4~5次大型洪水,洪水的重现期为0.71 ka。洪水事件主要发生在比较湿润的气候背景下,高频率洪水事件的发生与气候频繁的干湿波动有关。

Pleoflood Sediment of Shagou River and Its Response to the Climate Change During Early Holocene

Fluvial deposited material can record climatic information and paleohydrological information. On the basis of field research, systematic sampling, testing the grain size, mineral composition, and pH value of ZJDZ section, sedimentary records of paleoflood in this section can be divided into three sections. Especially the grain size parameters and the pH value in the second section fluctuate severely, representing different periods and different scales of flood, and the high frequency. Combined with six ¹⁴C data, a time scale is established: there are many large flood events occurred in the Shagou River during 10.9-4.0 kyr B.P. period, of which 20 times of large-scale floods occurred during 10.9-7.0 kyr B.P. period, flood recurrence interval is 0.40 kyr, which the flood-scale increase successively during 10.9-9.0 kyr B.P., during the 9.0-7.0 kyr B.P. period, the flood-scale has reduced; during the 7.0-4.2 kyr B.P. period, there are at least 4 to 5 large-scale flood, the flood recurrence interval is 0.71 kyr. Contrasting to the existed climate data, it is discovered that flood events occurred mainly in the background of relatively humid climate, high-frequency flood events are related to the frequent fluctuation in wet and dry climate.